Sound screening device for hydrophones



May 12, 1931. L. H. RICHMOND SOUND SCREENING DEVICE FOR HYDROPLANES Filed March 29 8 2 Sheets-Sheet 1 y 1931. L H. RICHMOND 1,805,186

SOUND SCREENING DEVICE FOR HYDROPLANES Filed March 29 1923 2 Sheets-Sheet 2 InZ'eIZZ'OW LE-c/v H. AP/cHMo/va Patented May 12, 1931 UNITED STATES PATENT GFFICE SOUND SCREENING DEVICE FOR HYDROPHONES Application filed March from one medium, through a second one, and

thence into the first one, depends upon the acoustic resistances of the two media. In general the transmission of sound energy will be great if the two media have approximately the same acoustic resistance, and

small if the two media have acoustic resistances of widely different values. With water as the first medium, and thus one acoustic resistance fixed, it becomes necessary in 5 providing a sound screen to select a medium whose acoustic resistance is widely different I from water.

With the foregoing and other objects in view, the invention consists in the combina tion of parts and in the details of construc' tion hereinafter described, certain embodiments of my invention being disclosed in the accompanying drawings, in which:

Fig. 1 is a bottom plan view of the sound screen with a diagrammatical showing of the position of the hydrophones.

Fig. 2 is a diagrammatical showing in perspective of a plurality of strips of fillers of fibrous material and the manner in which they are arranged with relation to each other before being introduced into the sound screen shell.

Fig. 3 is a view in front elevation of the ,5 sound screen facing in the direction of the source of sound to be detected.

Fig. 4i is a perspective view of the sound screen with the top portion removed.

Fig. 5 is a cross sectional view of Fig. 1.

Referring more particularly to the drawings, the device comprises an upper circular 1928. Serial No. 265,671.

wall Z with a semi-circular wall "X extending at right angles, thereto and conforming with the periphery of the wall Z. Another wall Y extends at right angles to the plane of the wall Z throughout the entire diameter thereof and is centrally disposed with relation to the arcuate wall X. The entire construction of the shell is of iron and is hollow, all of the walls being integral with each other and communicating.

it can be shown that a sheet of air of from two to three inches depth will allow considerably less than one per cent of the sound energy to pass from water through this layer of air to water on the other side, except for certain critical frequencies, at which or near which the transmission of sound energy is approximately equal to unity.

Ihave found that a means to escape this selective transmission is to introduce still another medium into parts of the'air space in such a manner as to break it up into sections.

Such a medium should have an acoustic resistance between air and water, and I have found it preferable to employ fibrous compo sition materials. This material is placed in the air space so that approximately the same amount of material and air is encountered as one passes through the air space from one side to the other.

The fibrous material is cut into thin sheets as shown at A. Sheet A is shown cut into a series of strips A with. the'ends A left uncut. I employ three more sheets which are identical. with A but the four sheets are arranged so that the strips of the adjacent sheets extend at right angles to each other. The spaces between the strips is approximately one and one-half inches.

The sheets of fibrous mater'al are placed in the hollow walls of the shell and on the upper face of the wall Z and the shell is then sealed by means of the cover 10 so as to be watertight. If so desired the sheets of fibrous material may be first inserted in watertight sheet metal casings or containers and the same then be placed in the shell in view of the difficulty of rendering the shell watertight. This arrangement, however,

does not alter the construction of the shell and is therefore not illustrated.

Vvhen the sound screen is assembled as described and the hydrophones H are placed in the positions indicated, the assembly is submerged in the water with the wall Z on top and the convex face of the wall X facing the shore. Thi the hydrophones are shieldfrom above by the wall Z, effectively shielded from below by the floor of the body of water, and from the sides by both the walls X and Y. The openings left between the walls X and Y face outwardly towards the body of water and this is left unshielded in order that the sound waves desired to be picked up by the hydrophoncs may readily be received thereby.

I Thus there is eliminated the undesired reccption of sound waves from the shore, from the surface waves above the hydrophones, an d furtherl nore sound waves not arising within a determinable sector at sea.

As analternative for the filler substance to be placed in the iron shell. I also propose the use of granulated cork. Furthermore, in view of the difficulty of providing a water- :tight shellI also propose to use as an alternative filler such substances as paratfine, ozite.

or tallow which when poured into the shell will solidify and make an effective shield.

Further as a substitute for the water tight compartment and for thefiller, a mass of hollow rubber tubing may bepaclred into the compartmentand bound together by pouring ozite, or similar substance around the tubing.

I claim: p

1. A sound screen comprising a hollow metallic shell having aplurality of sheets of fibrous substance introduced therein, said sheets being cut into spaced strips and arranged in such a manner thatthe strips of adjacent sheets are arranged atright angles to each other.

2. A sound screen comprising a hollow metallic shell having a fibrous substance introduced therein,said shell comprising a flat circular top, a semicircular side wall and avertical wall extendingthroughout the diameter of the top, all of which shell is integrally constructed. Q

3. A sound screen comprising a hollow metallic shell having a plurality of sheets of fibrous substance introduced therein, said shell comprising a flat circular top, a semicircular side wall and a vertical wall extending throughout the diameter of-the top, all of which shell is integrally constructed.

4. A sound screen comprisinga hollow metallic shell having a plurality of. sheets of fibrous substance introduced therein, said sheets being cut into space'dstrips, said shell comprising a flat circular top, a semicircular side wall and ,a vertical .wall extending throughout-the diameter of the top, all of hich shell isz integrally constructed.

of the top, all of which shell is integrally constructed.

6. A sound screen comprising a hollow metallic shell with a medium thereln of an acoustic resistance quality intermediate of said shell and its surrounding medium, said shell comprisinga fiat circular top, a semicircular side wall and a verticalwall 6X- tending throughout the diameter of the top, all of which shell is integrally constructed.

7. A sound screen for hydrophones comprising a hollow metallic shell having a fibrous substance introduced therein, said shell comprisinga fiat circular. top, a semicircular side wall and a vertical wall extending: throughoutthe diameter of the top, all of which shell isintegrally constructed, said hydrophones being placed on either side of said-'verticalwall, interior-of said semicircular wall and below said top.

.8. A sound screen for hydrophones com-F ,prising a hollow metallicshell having a pluralityof sheets of fibrous substance introduced thereiinsaid shell comprising aflat circulartop, .a semicircular side wall. and a vertical wallextending throughout the di-i duced therein, saidsheets-being cut into spacedstrip's, said shell comprising a'flat circular top, a semicircular side walland a vertical wall extending throughout the diameter ofthe top, all of which shell is integrally constructed, said hydrophones being placed on either side of said vertical Wall, interior of said semi-circular wall and'below said-top.

10. A sound screenforhydrophones coinprising ahollow metallic shell having a plurality of sheets" of fibrous substance intro-- duced therein, said sheets being cutinto spaced stripsandarranged in sucha manner that the stripsof adjacent sheets are aranged at right angles to each other, saidshell comprising a fiat circulartop, asemicircular side wall and a vertical wall extending h ldr'ophones being placed {on 'ieithersside 20f ameter of the top, allofiwhich shell is integrally constructed, said hydrophonesbeing placed on either side of said vertical wall, interior of said semi-circular wall and below said vertical wall, interior of said semicircular wall and below said top.

11. A sound screen for hydrophones comprising a hollow metallic shell with a medium therein of an acoustic resistance quality intermediate of said shell and its surrounding medium, said shell comprising a flat circular top, a semicircular side wall and a Vertical wall extending throughout the diameter of the top, all of which shell is integrally constructed, said hydrophones being placed on either side of said Vertical wall, interior of said semicircular wall and below said top.

In testimony whereof I aifix my signature.

LEON H. RICHMOND. 

